/* certinfo.c  --  Functions to parse and process the X509 TLS id string
 *
 *  GPLv2 only - Copyright (C) 2008 - 2012
 *               David Sommerseth <dazo@users.sourceforge.net>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; version 2
 *  of the License.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 */

/**
 * @file   certinfo.c
 * @author David Sommerseth <dazo@users.sourceforge.net>
 * @date   2008-08-06
 *
 * @brief  Functions for parsing X.509 subject information
 *
 */


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/x509.h>

#include <eurephia_nullsafe.h>
#include <certinfo.h>

/**
 * Simple strcmp() wrapper, which makes it NULL safe.
 *
 * @param s input value
 * @param v compare value
 *
 * @return Returns 1 if s and v are equal, otherwise 0.
 */
#define comp_attrib(s, v) ( (v == NULL || strlen_nullsafe(v) < 1) ? 0 : (strcmp(v, s) == 0) )

/**
 * Parses a X.509 subject string into a certinfo structure
 *
 * @param input  String containing a X.509 subject line
 *
 * @return Pointer to a certinfo structure containing the information
 */
certinfo *parse_tlsid(const char *input, const char *digest) {
        char tmp[130], *mainp, *origptr, *sub, *tok, *tok2;
        certinfo *ret = NULL;

        if( (input == NULL) || strlen(input) < 5)
                return NULL;

        ret = (certinfo *) malloc_nullsafe(NULL, sizeof(certinfo)+2);
        memset(&tmp, 0, 130);

        mainp = strdup(input);
        origptr = mainp;
        tok = strsep(&mainp, "/\0");
        while( tok != NULL ) {
                if( (tok != NULL) && (strlen(tok) > 0 ) ) {
                        sub = strdup(tok);
                        tok2 = strsep(&sub, "=\0");

                        if( comp_attrib("O\0", tok2) ) {
                                ret->org = strdup(strsep(&sub, "=\0"));
                        } else if( comp_attrib("CN\0", tok2) ) {
                                ret->common_name = strdup(strsep(&sub, "=\0"));
                        } else if( comp_attrib("emailAddress\0", tok2) ) {
                                ret->email = strdup(strsep(&sub, "=\0"));
                        }
                        if( tok2 != NULL ) {
                                free(tok2); tok2 = NULL;
                        }
                }
                tok = strsep(&mainp, "/\0");
        }
        free(origptr); mainp = NULL; origptr = NULL;

        /* Copy over the digest info */
        ret->digest = digest;

        /* Make sure we at least have empty NULL terminated strings */
        if( ret->org == NULL ) {
                ret->org = strdup("\0");
        }
        if( ret->common_name == NULL ) {
                ret->common_name = strdup("\0");
        }
        if( ret->email == NULL ) {
                ret->email = strdup("\0");
        }

        return ret;
}

/**
 *  Parses an X.509 certificate data structure into a certinfo struct
 *  This implementation depends on OpenSSL
 */
certinfo *parse_x509_cert (X509 *cert)
{
        int i, n, objnid;
        const int hashlen = SHA_DIGEST_LENGTH*3+2;
        ASN1_OBJECT *asn1 = NULL;
        ASN1_STRING *asn1val = NULL;
        X509_NAME *x509_name = NULL;
        X509_NAME_ENTRY *ent = NULL;
        const char *objbuf = NULL;
        unsigned char *buf = NULL;
        char *ptr = NULL;
        certinfo *ret = NULL;

        ret = (certinfo *) malloc_nullsafe(NULL, sizeof(certinfo)+2);

        x509_name = X509_get_subject_name(cert);
        n = X509_NAME_entry_count(x509_name);
        for (i = 0; i < n; i++) {
                ent = X509_NAME_get_entry(x509_name, i);
                if( !ent ) {
                        continue;
                }

                asn1 = X509_NAME_ENTRY_get_object(ent);
                if( !asn1 ) {
                        continue;
                }

                asn1val = X509_NAME_ENTRY_get_data(ent);
                if( !asn1val ) {
                        continue;
                }

                objnid = OBJ_obj2nid(asn1);
                if( objnid == NID_undef ) {
                        continue;
                }

                objbuf = OBJ_nid2sn(objnid);
                if( !objbuf ) {
                        continue;
                }

                if( ASN1_STRING_to_UTF8(&buf, asn1val) <= 0 ) {
                        continue;
                }

                // At this point we now have the 'field name' from the certificate
                // available in objbuf and the 'field value' in buf.

                if( (ret->org == NULL) && (strcmp(objbuf, "O") == 0) ) {
                        ret->org = strdup_nullsafe((char *) buf);
                } else if( (ret->common_name == NULL) && (strcmp(objbuf, "CN") == 0) ) {
                        ret->common_name = strdup_nullsafe((char *) buf);
                } else if( (ret->email == NULL) && (strcmp(objbuf, "emailAddress") == 0) ) {
                        ret->email = strdup_nullsafe((char *) buf);
                }
                OPENSSL_free(buf); buf = NULL;

                if( ret->org && ret->common_name && ret->email ) {
                        // If we got all we need, skip the rest
                        break;
                }
        }

        // Extract the SHA1 certificate fingerprint/digest
        ptr = ret->digest = malloc_nullsafe(NULL, hashlen);
        buf = cert->sha1_hash;
        for( i = 0; i < SHA_DIGEST_LENGTH; ++i ) {
                snprintf(ptr, 4, "%02x:", buf[i]);
                ptr += 3;
        }
        *(ptr-1) = 0;

        return ret;
}

/**
 * Frees up the memory used by a certinfo structure
 *
 * @param p Pointer to a certinfo structure to be freed
 */
void free_certinfo(certinfo *p) {
        if( p == NULL )
                return;

        if( p->digest != NULL )
                free(p->digest);
        if( p->org != NULL )
                free(p->org);
        if( p->common_name != NULL )
                free(p->common_name);
        if( p->email != NULL )
                free(p->email);

        free(p);
}